Concerning motors mainly used for industrial devices, it is desired to provide small and highly efficient motors so as to reduce electric power consumption. In order to accomplish the above object, highly efficient small motors are mainly used in which an iron core of a stator is divided by the teeth unit and concentrated winding is wound around the divided iron core so that a space factor of a slot winding can be enhanced and a space necessary for a winding end portion can be reduced.
Concerning the engineering method in which a certain number of the divided iron core sheets, which are made by punching an electromagnetic steel sheet, are laminated and fixed on each other so as to obtain this divided stator iron core, the following engineering methods are well known. They are as follows: an engineering method (a first engineering method) in which the divided iron core sheets are laminated on each other and the inner and outer circumferential faces are subjected to laser welding in a laminating direction; an engineering method (a second engineering method) referred to as a dowel caulking method or a PAC (Press Auto Clamp) system, in which a protruding portion and a recessing portion, which are made by conducting half blanking on the divided iron core sheet in the laminating direction, are engaged with each other and an upper core and a lower core are connected with each other by means of caulking; and an engineering method (a third engineering method) in which electromagnetic steel sheets for adhesion iron cores are used as the divided iron core sheets and laminated and fixed to each other by pressuring and heating (thermal-pressure bonding). This third engineering method is disclosed in the Japanese Patent Unexamined Publication No. H11-162722.
In the first engineering method, the following problem may be encountered. An eddy current loss is caused on a surface facing a permanent magnet of a rotor. Therefore, a motor efficiency is deteriorated. In order to reduce this eddy current loss, a method is proposed in which the divided iron core sheets are laminated and then integrated with each other into one body by means of resin. This method is disclosed in Japanese Patent Unexamined Publication No. 2000-333388. Even in the second engineering method, an eddy current loss is caused at an engagement portion in which a protruding portion and a recessing portion made by half blanking are engaged with each other.
According to the third engineering method, it is possible to reduce the aforementioned eddy current loss. However, commonly used electromagnetic steel sheets, which are used for the other engineering methods, are coated with inorganic coating material. On the other hand, in the case of the above engineering method, in order to ensure the adhesion strength, film thickness of coating used for adhesion of the electromagnetic steel sheets for the iron core is increased. Therefore, a quantity of iron per unit lamination length is lowered, that is, a space factor of the iron core is lowered. In general, a cost of this electromagnetic steel sheet used for adhesion iron core is higher than a cost of the electromagnetic steel sheet on which inorganic coating material is coated. Accordingly, the cost of the divided fixing iron core is raised.
In the conventional stator and the engineering method of manufacturing the stator, the following problems may be encountered when the divided iron core sheets are laminated and fixed. That is, an eddy current loss of the laminated iron core obtained by the laser welding or the dowel caulking system is large. A space factor of the laminated iron core obtained by the adhesion lamination engineering method is low and the manufacturing cost is high.
When the divided iron sheets are taken out without laminating and fixing them in a metallic die right after the divided iron sheets have been punched out with a punching die, the iron cores are discharged from the metallic die being separated from each other. Therefore, it becomes necessary to arrange the iron cores so that directions and both sides of the iron cores can be made to be proper. Accordingly, it takes much labor to arrange the iron cores for lamination.